President Carter asked the American people last night to band together and be prepared to accept some "mutual sacrifices," beginning with a conservation program to overcome the nation's growing energy problems.

In remarks prepared for delivery at a televised address from the White House library, the President bluntly warned that the nation's energy shortage is permanent and will be kept tolerable only if "we all cooperate and make modest sacrifices."

"There is no way that I, or anyone else in the government, can solve our energy problems if you are not willing to help," he said. ". . . There is no energy policy we can develop that would do more good than voluntary conservation."

Planned as an informal "conversation" with the American people, the talk was Carter's first address to the nation since his inauguration. He used it to reiterate many of his campaign promises, among them efforts to reorganize the federal government, stimulate the economy and to seek comprehensive tax and welfare reform.

But the address was cautious in tone and the President conceded that much of what he seeks to accomplish will take time and the close cooperation of Congress and the American people.

In his first two weeks in office, Carter said, he has already learned that "there are many things a President cannot do" but that he remains optimistic about the future.

Calling for a renewal of faith in "joint efforts and mutual sacrifices," the President said: "But while he will never please everyone "you will never have the feeling that your needs are being ignored, or that we have forgotten who put us in office."

As White House aides have been predicting all week, Carter made no major new policy pronouncements in the talk. Two new innovations he did announce were that he will soon put a ceiling on the number of employees in government agencies and that he will require future government regulations to bear the names of their authors.

But for the most part, the talk dealt with administration, objectives that have already been oulined, with special emphasis given to energy and the economy.

As the President spoke, much of the Eastern half of the nation was suffering from the effects of the brutally cold weather and a severe distribution shortage of natural gas. Carter referred to this, but said "the real problem - our failure to plan for the future or to take energy conservation seriously - started long before this winter and will take much longer to solve."

The President promised to complete planning of a national energy policy by April 20 and said that it will "emphasize conservation."

"The amount of energy now being wasted which could be saved is greater than the total evergy we are importing from foreign countries," he said.

The program will also stress development of the nation's coal reserves - including support for congressional strip mining legislation - research on solar energy and other "renewable energy sources" and the maintainence of "strict safeguards on necessary atomic energy production," Carter said.

While calling for individuals to make "modest sacrifices" to conserve energy, the President also asked utility companies to "promote conservation and not consumption" and said that oil and natural gas companies "must be honest with the people about their reserves and profits."

"We will find out the difference between real shortages and artificial ones," he said.

Speaking of government reorganization, the President recalled some steps he has already taken, including an order to reduce the size of the White House staff and the elimination of "expensive and unnecessary luxuries" such as limousine service for high ranking officials. He specifically asked that people not send gifts to him and his family.

"Government officials can't be sensitive to your problems if we are living like royalty here in Washington," Carter said.

The administration is expected to take the first step toward reorganization today with the introduction of authority to implement reorganization plans subject to congressional vetoes.

Reorganization itself, the President said last night, will include zero-based budgeting - under which government agencies must regularly justify ongoing programs - a reduction in the number of government regulations and so-called "sunset laws" that would cancel programs that no longer are considered useful.

On some of his other major domestic objectives, Carter:

Defended his proposed $31.2 billion economic stimulus package, which he called "the best-balanced plan we can produce for the overall economic health of the nation."

Promised to produce before the end of the year a comprehensive reform proposal for a "fairer, simpler" tax system.

Said that within 90 days the administration will issue its first report on proposals for welfare reform that are aimed at developing "a new system which will minimize abuse, strengthen the family and emphasize adequate support for those who cannot work and training and jobs for those who can."

The President touched only briefly on foreign policy in the talk, pledging to maintain a strong national defense.

"Our policy should be based on close cooperation with our allies and worldwide respect for human rights, and it must always reflect our own moral values," he said. "I want our nation's actions to make you proud."